The overall goal of this SBIR Phase II program is to continue development and commercialization of a new class of gas sensor under development by KWJ Engineering, Inc. (KWJ) to ozone monitoring and the implementation of a new home ozone alarm based on this technology. This Phase I program is directly related to the mission of NIEHS, as it aims to reduce of the burden of human disease and dysfunction arising from environmental causes by providing a reliable means for at-risk populations to be aware of unhealthy ozone conditions in their homes. We will demonstrate the application of this new gas sensor, a very small, ultralow power, high reliability printed electrochemical sensor, for development of a home ozone (O3) alarm for individuals with respiratory diseases and all those concerned about their exposure to ozone. This alarm will help those with respiratory conditions to manage their health by alerting them to ozone conditions that may exacerbate respiratory problems or pose danger to life and health. Over 118 million people in the United States live in areas of nonattainment of the EPA 8 hour ozone standard. The potential for development of asthma and other respiratory conditions, as well as aggravation of existing respiratory conditions among at-risk groups including the elderly and children in such high ground level ozone areas calls for a practical home ozone monitor, similar to the carbon monoxide monitors that are now commonplace in the home. KWJ's new class of amperometric gas sensor, the screen-printed electrochemical sensor (SPEC), will deliver high performance gas sensing for a wide range of applications at commodity-level prices. These devices, which are about the size of a dime, are able to use a variety of conventional and developmental electrolytes. This provides unprecedented access to a wide range of tunable selectivity, sensitivity and robustness to environmental conditions compared to conventional sensors. The Phase I program involved fabrication and testing of SPEC devices with demonstration that new electrodes and electrolytes could be used to produce sensor with better sensitivity, detection limit, stability and reliability that current commercial sensors. These sensors were validated vs. standard UV spectrometric ozone measurement and demonstrated successfully as the transducer for actuation of a home ozone alarm demonstration, with ozone concentrations relevant to health concerns (0 to 130 ppb). Phase II will complete development of the sensor, particularly its rational design based on the electrolytes and catalysts, and will produce prototype ozone alarm units to be tested and validated with our industrial partners.